It has been proposed to add nanoparticles having nanometer-sized diameter in a heat transport fluid that absorbs and transports heat from a heat source so as to improve heat conductivity of the heat transport fluid. Such a heat transport fluid is, for example, described in JP2007-31520A (hereinafter, the document 1) and JP2008-189901A corresponding to US2010/0095911A1 (hereinafter, the document 2).
In the heat transport fluid of the document 1, 0.05 or more mass % carbon nanotubes and cellulose derivative or sodium salt thereof are added in a base liquid such as water or ethylene glycol. In the heat transport fluid of the document 2, carbon nanotube and sodium carboxyl methyl cellulose whose average molecular weight given by GPC measuring method is 6000-30000 are added in a base liquid such as water or ethylene glycol.
When the heat transport fluid of the document 1 or the document 2 is used in a closed heat transport circuit for facilitating heat exchange, the fine particles contained in the heat transport fluid may adsorb to a surface of a passage or a device of the heat transport circuit. As a result, an adsorption layer will be formed.
Therefore, in a location where the adsorption layer is formed, a heat transfer coefficient is reduced due to the adsorption layer increasing heat-transfer resistance. Further, in the passage having a small sectional area, the adsorption layer causes clogging and an increase in pressure loss, resulting in degradation of efficiency.